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<!----------------------------------------------------------
 
	Copyright (c) 2015-2018 Jean-Marc VIGLINO, 
	released under CeCILL-B (french BSD like) licence: http://www.cecill.info/
	
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	<title>ol-ext: hash lines example</title>
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	<meta name="description" content="an OL3 stroke style with a set of cartographic patterns to use in your maps." />
	<meta name="keywords" content="ol3, vector, style, stroke, fill, pattern, hatch, hatching" />

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	<a href="https://github.com/Viglino/ol-ext" class="icss-github-corner"><i></i></a>

	<a href="../../index.html">
		<h1>ol-ext: hash lines example</h1>
	</a>
	<div class="info">
		<p>
			This example use the <i>ol.geom.offsetCoords()</i> function to draw an offset line with a dash symbol.
		</p>
		<p>
			NB: some problem may occur when offsetting lines with acute convex angles... 
			You should probably look at <a href="https://openlayers.org/en/latest/examples/jsts.html">JSTS</a> to handle this cases.
		</p>
	</div>

	<!-- Map div -->
	<div id="map" style="width:600px; height:400px;"></div>

	<div class="options" style="min-width:300px;">
		<h2>Options:</h2>
		<ul>
			<li>
				Draw:
				<label>
					<input type="radio" name="op" value="drawPoly" /> 
					Polygon
				</label>
				<label>
					<input type="radio" name="op" checked="checked" value="drawLine" /> 
					LineString
				</label>
				<label>
					<input type="radio" name="op" value="modify" /> 
					Modify
				</label>
			</li>
			<li>
				<hr/>
				Offset: <input id="offset" type="number" value=5 onchange="vector.changed()" />
			</li>
		</ul>
	</div>
	
<script type="text/javascript">
	
	// Layers
	var layer = new ol.layer.Tile({
		title:'terrain-background',
		source: new ol.source.Stamen({ layer: 'terrain' })
	});

	// The map
	var map = new ol.Map({
		target: 'map',
		view: new ol.View
		({	zoom: 5,
			center: [166326, 5992663]
		}),
		layers: [layer]
	});

	// Offset geometry
	function offsetGeometry (feature, size) {
		switch (feature.getGeometry().getType()) {
			case 'Polygon':
				var coords = feature.getGeometry().getCoordinates();
				var sign = feature.getGeometry().getLinearRing(0).getArea()<0 ? -1:1;
				coords[0] = ol.coordinate.offsetCoords(coords[0], sign*size);
				return new ol.geom.Polygon(coords);
			case 'LineString':
				var coords = feature.getGeometry().getCoordinates();
				coords = ol.coordinate.offsetCoords(coords, size);
				return new ol.geom.LineString(coords);
			default:
				return feature.getGeometry();
		}
	}
	
	// Style function with offset hash
	function getStyle(feature, res){
		var offset = parseInt($("#offset").val());
		return [ 
			new ol.style.Style({
				stroke: new ol.style.Stroke({	
					width: 1.5,
					color: "#8B4513"
				})
			}),
			new ol.style.Style({
				stroke: new ol.style.Stroke({	
					color: "#8B4513",					
					width: offset>0 ? 2*offset : -2*offset,
					lineDash:[1.5,10],
					lineCap:'butt',
					lineJoin:'bevel'
				}),
				// Offset geometry
				geometry: function (feature) { return offsetGeometry(feature, offset*res); }
			})
		];
	}

	// Nouvelle source de donnee
	var vector = new ol.layer.Vector({
		source: new ol.source.Vector({ features: new ol.Collection() }),
		style: getStyle
	})
	map.addLayer(vector);
	vector.getSource().addFeature(new ol.Feature(new ol.geom.Polygon([[[259274, 6398696], [63595, 5958419], [635956, 5772524], [259274, 6398696]]])));

	// global so we can remove it later
	var interactions = {
		select: new ol.interaction.Select (),
		modify: new ol.interaction.Modify ({ features: vector.getSource().getFeaturesCollection() }),
		drawLine: new ol.interaction.Draw({
			type: 'LineString',
			source: vector.getSource()
		}),
		drawPoly: new ol.interaction.Draw({
			type: 'Polygon',
			source: vector.getSource()
		})
	}
	for (var i in interactions) map.addInteraction(interactions[i]);

	// Activate interaction
	setInteraction = function ()
	{	//interactions.select.getFeatures().clear();
		var name = $('[name="op"]:checked').val();
		for (var i in interactions) 
		{	interactions[i].set("active", (i==name));
		}
	}
	setInteraction();
	$("input:radio").on("change",setInteraction);

</script>

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